ASRock Extreme4 X79 - 'Mac OS Version not yet set' - I'm stumped!

The Extra folder contained a special set of kexts that allow you to boot with fewer problems. You deleted those when you replaced the Extra folder. A common problem for an Asus is to have a kernel panic on the AppleIntelCPUPowerManagement.kext. The Extra folder contained a kext named NullCPUPowerManagement.kext that would have fought that panic.

I would suggest you remake the Unibeast USB drive and use it as built. Even if it means a couple of BIOS edits right now.

If you get the kernel panic again, boot in verbose mode (-v) and when the text stops scrolling, snap a picture and post it.